Methods: In the present study, 176 infants and young children with AD aged under 6 years living in Seoul Metropolitan Area in Korea were enrolled and were followed for 17 months between August 2013 and December 2014. AD symptoms describing the degree (a scale of 0 to 4) of itching, sleep disturbance, erythema, dryness, oozing, and edema were recorded on a daily basis. Generalized linear mixed models (GLMM) with binomially distributed errors were used to estimate of the effects of meteorological factors (daily mean temperature, relative humidity, and diurnal temperature range (DTR)) and air pollutants (PM10, nitrogen dioxide (NO2), and ozone) on the AD symptoms. Potential confounding factors including age, sex, symptom severity (SCORAD) at initial visit, the presence of fever, and day of week were controlled. Moving averages up to previous 5 consecutive days were used to represent the lag effect of meteorological variables and air quality on AD symptoms.
Results: Of the 34,978 person-days, the rate of positive AD symptoms was 44.12% during the study period. Increase in daily mean temperature by 5 ºC and relative humidity by 5% were significantly associated with 13.36% (95% CI: 11.03 to 15.63) and 2.70% (95% CI: 1.25 to 4.14) of decrease in AD symptoms, respectively. Particularly in spring, an increase in 5 ºC of DTR was related with 53.26% (95% CI: 12.39 to 108.99) of increase in AD symptoms when the effect of moving average from the same day through previous three consecutive days was estimated. An increase in 10 µg/m3 of PM10 concentration increased 2.95% of AD symptoms (95% CI: 1.35 to 4.5). An increased concentrations in 10 ppb of NO2 and ozone were associated with increase in AD symptoms by 4.31% (95% CI: 0.75 to 7.99) and by 5.55% (95% CI: 2.78 to 8.39), respectively. The hazardous effect of PM10 on AD symptoms was noted significantly in spring and those of NO2 and ozone were found in winter.
Conclusions: Short-term exposure to temperature, humidity, and air pollutants are strongly associated with the AD symptoms. Clean air quality is essential for the appropriate management of AD symptoms in children.